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UNITED STATES ATENT FFIcE.

AMZI L. BARBER, OF WASHINGTON, DISTRICT OF COLUMBIA.

CONCRETE PAVEMENT.

SPECIFICATION forming part of Letters Patent No. 391.222, dated October 16, 1888.

Application filed Ju y 18, 1888. Serial No. 280,328.

To all whom it may concern.-

Be it known that I, AMZI L. BARBER, a citizen of the United States of America, residing at Washington, in the District of Columbia, have invented certain new and useful Improvements in Concrete Pavements, of which the following is a specification.

My invention relates to improvements in concrete pavements, and more particularly is an improvement on the invention of E. J. De Smedt, patented December 20, 1887, No. 375,273.

The object of my invention is to thoroughly lock or cement the different layers or strata of which the pavement is composed, so that there will be less liability to crack and disingrate under the influence of the heat, cold, or moisture.

My invention consists, therefore, of a pavement having a base or foundation layer of broken stone or gravel coated with a coaltar paving-cement, upon which is placed a second and intermediate layer of smaller broken stone coated with coal-tar, upon which is placed the wearing course or layer of asphaltum, heavy petroleum, or the residuum of petroleum, and fine sand.

In carrying out my invention the road-bed is excavated to the proper depth, preferably about six inches below the surface of the pavement when completed, upon which is laid a foundation-layer of coarse broken stone or gravel about three inches in depth, (more or less,) said broken stone being coated with hot coal-tar, preferably a cement of what is known to the trade as No. 4 coal-tar distillate, in the proportion of about one gallon of the cement to each square yard of pavement. This base or foundation layer is well rolled and rammed with a steam-roller, so that when compacted itwill be about threeinches in thickness, (more or less,) as above stated.

The second or hinder course is composed of clean broken stone or gravel, not exceeding one and one-fourth (ll) inch in largest dimensions, the stone to be heated in any suitable manner and mixed with No. 4: coal-tar, distillate in the proportion of aboutone (1) gallon of the distillate to one (1) cubic foot of stone. This binder-course is spread on the base or foundation course to form a layer of about one and one-half (1%) inch in thickness when properly rolled or compacted. In

(No specimens.)

preparing the broken stone for this second or binder course care should be exercised to coat each individual stone thoroughly, so that they will be cemented to the base-course and to each other when properly laid. This coating of the broken stone with the cement is best effected bythe use of suitable mixing machinery.

The top or wearing surface or course is next placed upon the binder-course, and is to be about one and one-half inch in thickness when compacted. This top or wearing surface is composed of refined Trinidad or other suitable natural asphaltum, heavy petroleum, or the residuum of petroleum, and fine sand.

The proportions of asphaltum andresiduum of petroleum or heavy petroleum-oil used may be varied within certain limits, but I prefer to use from fourteen to seventeen parts of residuum of petroleum to each one hundred parts of asphaltum, and sand sufficient to take up the bituminous compound and form a solid mass when cold, and the sand and the asphaltic cement formed by the union of the asphalt and residuum are heated separately prior to being mixed.

The materials and combination of materials forming each layer or course of the pavement, except the first one of broken stone, are laid while in a heated condition, so that the second or binding course is joined or cemented to the base or bottom course and the top or wearing course is cemented to the intermediate or binding course, and in this manner I produce a pavement which will be solid in all its parts and capable of withstanding the action of water and the expansions and contractions incident to thermal changes.

Having thus described my invention, what I claim is- A concrete pavement consisting of a base or foundation layer of broken stone coated with coal-tar or a coal-tar distillate, a binder or intermediate layer of smaller broken stone similarly coated, and a top or wearing course com posed of asphaltum, residuum of petroleum, and sand, substantially as set forth.

In testimony whereofI affix my signature in presence of two witnesses.

AMZI L. BARBER.

Vitnesses:

HENRY J. KEARNEY, J OHN I. WHITEHORN. 

